This question is about acids - AQA - GCSE Chemistry - Question 9 - 2021 - Paper 1

The solution with 1.0 mol/dm³ hydrogen chloride solution would have the lowest pH since it has the highest concentration of H⁺ ions.

1. Swirl the solution during titration to ensure proper mixing of the reactants.
2. Use a white tile under the flask during titration to better observe the endpoint color change.

To find the mass, first calculate the number of moles needed:

ext{Moles} = ext{Concentration} imes ext{Volume} = 0.0480 imes rac{250}{1000} = 0.0120 ext{ mol}

Next, calculate the mass using the molar mass:

$ext{Mass} = ext{Moles} imes ext{Molar Mass} = 0.0120 imes 90 = 1.08 ext{ g}$

Using the reaction stoichiometry, we can determine the moles of H₂C₂O₄ first:

ext{Moles of H₂C₂O₄} = 0.0480 imes rac{15.00}{1000} = 0.00072 ext{ mol}

Since 1 mole of H₂C₂O₄ neutralizes 2 moles of NaOH,

$ext{Moles of NaOH} = 2 imes 0.00072 = 0.00144 ext{ mol}$

Now, calculate the concentration:

ext{Concentration} = rac{ ext{Moles}}{ ext{Volume}} = rac{0.00144}{0.0250} = 0.0576 ext{ mol/dm³}